DENBIGHSHIRE GRITS, NEAR CORWEN, NORTH WALES. 483 



to the Coniferce, but yet differing from any Conifer known to him 

 " in the cylindrical form and loose aggregation of the wood cells, as 

 seen in the cross section, in which particular it more nearly resem- 

 bles the young succulent twigs of some modern Conifers than their 

 mature wood." He maintained, however, that it was an " exogenous 

 tree, with bark, rings of growth, medullary rays, and well-developed 

 though peculiar woody tissue "*. 



Mr. Carruthers subsequently examined the same plant and re-de- 

 scribed it in an elaborate paper in the Monthly Microscopical Journal 

 for October 1872, and gave numerous reasons for excluding it not only 

 from the Coniferse, but from land plants altogether, and for placing 

 it in preference among the Algae. In doing so, however, he said it 

 was an " anomalous Alga, and, indeed, that with the materials 

 known, it was not possible to correlate it with certainty with any 

 known group of Algae." The identity of our plant with the above 

 mentioned, which was re-named by Mr. Carruthers Nematophycus, 

 is placed beyond doubt by the following note kindly given me 

 by Mr. Carruthers : — 



" The slides prepared by Mr. Newton show clearly that his deter- 

 mination of the fragments of charcoal and petrified remains of plants 

 in the Silurian rocks which you have found, belong to the same type 

 of plants as that discovered by Logan at Gaspe, in beds which he 

 considered to be of Devonian age. This was described by Principal 

 Dawson in the Quart. Journ. Geol. Soc. (vol. xv.) under the name Pro- 

 totaxites Logani. I made a careful examination of specimens which 

 I owed to the kindness of Dr. Dawson, and published the results of 

 this examination in the Monthly Microscopical Journal, giving the 

 reasons for placing it among cellular plants and naming it Nemato- 

 phycus Logani. The specimens show very distinctly the larger 

 tubes of Nematophycus, running generally in a subparallel direction, 

 but passing in and out amongst each other. The walls are not in juxta- 

 position, leaving free space all around them, which was occupied, as 

 is shown in the better-preserved specimens from Gaspe, with a dense 

 tissue of more delicate tubes of smaller dimensions. That your speci- 

 mens belong to the plant called Nematophycus I have no doubt. The 

 conditions under which they are found are very different from those 

 described by Dr. Dawson. His specimens were large trunks, some- 

 times perfectly silicified and preserving their most minute structures. 

 Your specimens, consisting of small fragments, consequently supply 

 no help to the further knowledge of this remarkable plant, unless 

 the occurrence on the same slab, in tolerable abundance, of small 

 round bodies having the same form and structure as those found in 

 the Ludlow bone-bed, which were figured and described by Sir J. 

 D. Hooker under the name Pachytheca, indicate some possible re- 

 lationship. The specimens found by you are perhaps smaller than 

 those from Ludlow. They present no indication of attachment, and 

 no evidence of their relation to Nematophycus, except their being 

 found together, which is not always a good basis for structural re- 



* ' American Naturalist,' vol. v. p. 245. 



